Lubricating oil



Patented June 22, 1937 UNITED STATES PATENT OFFICE lon, Roulle Park, N.

J., assignors to Standard Oil Development Company, a corporation of Delaware No Drawing. Application December 22, 1932, Serial No. 648,445

12 Claims. (01. 196-151) The present invention relates to improvements in the art of producing oils oi low pour point and more specifically to improved methods for reducing the pour point of wax-containing lubricating oils by the use of pour inhibitors. The invention will be fully understood from the following description of the method and products obtained thereby.

Petroleum fractions of the type used for lubricating oils frequently contain a suflicient amount of solid wan constituents to cause the oil to congeal or solidify at temperatures of 25, 30, 40 F., or even higher and but for this fact these oils would be suitable as lubricants at temperatures far below. The lubricating quality of the oil is not improved by the removal of the wax and the operation is expensive since it requires refrigeration especially when removal is suiiiciently complete to produce oils pouring at 0 F. or below. The problem of making low pour oils from wax containing oil without the removal of the waxy constituents has been met by the use of pour inhibiting agents, which substances may be added to the oil in small amounts to prevent solidification of the oil at its normal v pour point and to cause it to pour at considerably lower temperature.

As a general rule, heavier oils are less susceptible to pour inhibitors than lighter fractions but in addition to this we have found that narrow cut oil fractions are less susceptible to the action of pour inhibitors than are oils of the same general viscosity range but produced by blending fractions of widely different viscosities. In general, we find that the straight out oils corresponding to the fractions generally obtained from the stills, and especially from fractionating stills, are too narrow in range to bring out the full capabilities of the inhibitors. The 40 lightest lubricating oils do not contain much wax and may have quite low pour points, but as viscosity increases pour points also rapidly rise. It is desirable to have a lower pour point than is obtained in the natural oil without wax separation, or with only partial wax removal but due to the fact that these normally narrow cut oils are less susceptible to pour inhibitors their pour points are generally reduced not more than 20 or 30 F., whereas blended oils produced by the 60 admixture of lighter and heavier fractions will be reduced by some or F. by the same pour inhibitor used in the same concentration. We are unable at present to state definitely the reason for this particular action and we do not 6 wish to be bound by any theory. at the same I time we wish to state merely the fact that the blends of widely diiierent oils differing in boiling range, viscosity and molecular weight are much more susceptible to pour inhibiting action than are the ordinary close out fractions.

The oils which we prefer to add to the spindle and neutral oils, for example, for the purpose of gaining increased pour depression are preferably those of the class known as bright stocks and produced by the reduction of crude oils either by fire and steam, or under vacuum, with subsequent filtration of the oil. It will be understood that these are not the only oils which exhibit this property but that they serve to illustrate our purpose. It is desirable to have a molecular weight range of to 200 or more, that is, to add oils whose average molecular weights differ by this amount. We prefer to use clean oils free of asphaltic or other colloidal matter, and the oils made by filtration through fullers earth or similar adsorbent materials, or by the treatment. with sulphuric acid, or a combination of these methods, are satisfactory.

These oils frequently contain considerable quantities of wax in an amorphous form, petrolatum, and consequently, have more or less high pour points unless they are specially dewaxed. We may use either the high pour oil or the dewaxed stock and, indeed, petrolatum derived from these oils appears to be equally useful for the purpose. The amount of heavier oil should always be less than the amount of spindle or neutral oil itself, but the amount may vary considerably and the pour point of the blend after the addition of the pour inhibitor appears to be an obscure function of the amount of the heavy oil. If too little is used the pour point is not depressed to its maximum and similarly if too much is used the pour point again rises. In general, we prefer to add from say 3 to 10% of the heavier oil and this will usually produce the minimum pour point, but this can be determined best by test samples from the particular oils mixed in different proportions. Considerably more may be added, for example 20% or even 50%, but since the heavier oils command higher prices than the neutrals and other lighter oils, it is generally desirable to limit the amount of the heavier oil to what is required for pour reduction. It will be understood, also, that the viscosity of the neutral oil is raised by the addition of the heavier oil. In order to minimize this increased viscosity it is desirable to use the least possible quantity of the heavier oil such as bright stock to effect the optimum pour reduction. Be-

sides the bright stocks we may use other oils which may not be made in precisely thesame manner but which have boiling ranges, viscosity range and molecular weight within the same general limits. Steam refined cylinder oils, or in fact any other heavy cut of a correspondingly higher molecular weight may be used for my purpose, although they may not be as desirable as the bright stocks.

We find it edually desirable to add a lighter oil to heavier oils where the pour points are to be reduced by inhibitors. For example, it is desirable to add to of a special heavy naphtha or light spindle oil or gas oil to cylinder stocks 5 so as to increase the molecular weight range and to increase the pour depressing effect.

The pour inhibitors we use may be made in various ways, but the preferred ones are pure hydrocarbons. They are preferably made by polymerization or condensation of the active derivatives of paraifin wax, petrolatum and similar waxy hydrocarbons. By active derivatives we intend to include the halogenated waxes or olefins derived from such halogenated waxes by dechlorination, or from the waxes themselves by vigorous dehydrogenation, in which there is the least possible disturbance of the original carbon structure of the wax. These materials may be condensed on themselves or on each other, or on other substances such as the aromatic hydrocarbons, hydro-aromatics, or hydroxyl, nitro and amino derivatives of such ring compounds. The condensation is carried out at low temperature, for example below 150 F. and preferably at about room temperature, through the agency of aluminum chloride, zinc chloride, or boron fluoride or their known equivalents.

Hydrocarbon pour inhibitors of the same: type may be produced by other means as well, for example by the action of high frequency electric current of high voltage and under reduced pressure. In this process the waxy hydrocarb on'is maintained in a fluid condition and is subjected in a known manner to the action of the rapidly oscillating electric current. The steps of this process are in general similar to the electrical condensation of mineral and vegetable oils known at the present time, but to obtain pour inhibitors waxy materials must be treated and the waxy 50 materials are preferably oil free. The waxes may be treated alone or they may be first converted to olefins or chlorinated and condensation may be in the presence or absence of materials of the ring structure, as indicated in the previous 55 pa agrap Another method of carrying out a condensation which will produce pour inhibitors is by the treatment of a waxy hydrocarbon with oxygen or air at low temperature. The air is blown 0 through the oil at a low temperature, say 100 to 160 F. A considerable quantity of the wax is oxidized to acids and similar products, and after distillation of the acids a high molecular weight polymer may be recovered as a residue which is 5 an active pour inhibitor.

Metallic salts such as the aluminum, zinc, nickel, cobalt, salts of heavier fatty acids and especially hydroxy acids such as hydroxy stearic acid, or of the acids made by the oxidation of 70 parafiin wax with air or nitric acid or similar means, are also pour inhibitors which may serve our purpose.

Other types of pour inhibitors which may. be used are the esters of the polyalkylolamines, for

75 example, diand triethanolamine stearate, also the oil-soluble cellulose derivatives containing hydrocarbon chains and which may be either others or esters. Polymerized products of unsaturated acids such as oleic acid or its esters, with or without aromatic materials such as naphthalene, and caused by polymerization catalysts generally and particularly of "the type of aluminum chloride, can be used for our purposes.

The action of all of the known types or pour inhibitors is improved in respect to the lighter oils of the class described by the addition of a small amount of the heavier oil of the type described and in the proportion described.

As an example of the effect of our discovery of the influence of the presence of heavier oil. the following tests are submitted.

In the following tests a straight out spindle oil and a straight cut bright stock obtained by the usual distillation methods, the characteristics of which are given in the table below, were mixed in different proportions as indicated, but in each case 1% of a pour inhibitor produced by the low temperature aluminum chloride condensation of halogenated paramn wax and naphthalene was used.

Spindle oil Bright stock Gravity 30. 9 26.5 A.P.I. Vis. at 100 F 156 secs. Say. 2,350 secs. Bay. Vis. at 210 F 151 secs. Say. Pour point 30F. 20 F. Flash 385 F. 550 F. Average mol. wt- 370 575 M01. wt.-F1rst 10 percent. 315 425 M01. wt.Last 10 percent. 410

Percent spindle oil ggg g Pour point As stated above, in each of the above cases 1% of the inhibitor was used.

When 2% of the inhibitor was used with 98% of a light neutral oil the pour point is found to be 10 F., but when a blend of 91% of a spindle oil, 8% bright stock and 1% of inhibitor is made, the pour point is found to be 15 F.

Using another fraction of the spindle oil type with a heavier oil which will be termed bright stock, the following results were obtained. In all of these cases /2% of active pour inhibitor was used.

Pour point sasssmssaso It is noted. that if the bright stock is in equal or greater proportion than the spindle oil, the pour point tends to rise and the minimum pour point is found generally to occur between 5 and 10% of the heavier oil.

In other tests instead of adding the bright stock itself, wax removed from a bright stock was added with similar results, for example, an oil with a pour point of 20 F. is reduced to 0 F. with 1% of an active pour inhibitor, but after the incorporation of 4% of a heavy petrolatum removed frcm a residual stock by cold centrifugal treatment, the pour point is found to be reduced to 30 F.

Our invention is not to be limited by any theory of pour reduction, nor to the use of any particular types of lighter and heavier oils nor, indeed, to any particular type of inhibitor, but only to the following claims in which we wish to claim all novelty inherent in our process.

We claim:

1. A low pour point lubricant, comprising a blend of two petroleum lubricating oils having average molecular'weights 'diflering by at least 150 and a pour inhibitor.

2. A low pour point lubricating oil, comprising a blend of a straight cut oil and a minor quantity of a heavier petroleum lubricating fraction having an average molecular weight greater by not less than 200, together with a pour inhibitor.

3. A low pour point lubricating oil, comprising a spindle oil with from 3 to of a natural bright stock and a hydrocarbon pour inhibitor.

4. A composition of matter comprising a neutral oil having a viscosity below 400 seconds Saybolt at F. with a minor proportion of a heavier natural oil having a viscosity in excess of 100 seconds at 210 F. and 8. Pour inhibitor.

5. A composition of matter according to claim 4 comprising a wax bearing neutral oil with a minor proportion of a bright stock having a viscosity between about and 1'15 seconds at 210 F. and a pour inhibitor.

6. A composition of matter comprising a wax bearing neutral oil having a. viscosity from about 60 to 400 seconds Saybolt at 100 F. with a minor proportion of a bright stock and a pour inhibitor.

7. A composition 01' matter comprising a spindle oil with a minor proportion of bright stock and a pour inhibitor of the type produced by the low temperature aluminum chloride'condensation of an active wax derivative.

8. Composition according to claim 1, in which the inhibitor is of the type produced by the condensation in presence of an aromatic hydrocarbon.

9. Composition according to claim 3, in which the amount of bright stock is between 5 and 10%.

10. An improved process for lowering the pour point of a narrow cut waxy oil comprising adding to such oil a substantial portion 0! another lubri cant which has an average molecular weight higher by at least than that of the said narrow cut oil, whereby the molecular weight range of the blend is'greatly increased, and adding a pour inhibitor thereto.

11. Process according to claim 10 in which the oil of higher molecular weight than the narrow cut oil is added in proportion of from about 3 to 50% of the blend.

12. Process according to claim 10 in which the narrow cut oil is a spindle oil and the other lubricant is a bright stock.

CHARLES C. SWOOPE. MARTIN M. SADLON. 

